This invention relates generally to athletic shoes, and, more particularly, to a non-absorbant, thermally non-conductive insert overlying the insole of an athletic shoe.
New designs of athletic shoes in recent years have provided improvements in the support, cushioning and stability of the shoe in an effort to reduce injuries to the feet, ankles and knees. One aspect of athletic shoe design which has been overlooked, however, is the configuration and surface characteristics of the insole of the shoe.
Most insoles of athletic shoes are formed of a cushioning material such as rubber, foam or the like whose uppermost surface is covered by cloth or leather which contacts the sock of the wearer's foot. One problem with this type of insole is that the rubber or foam absorbs moisture from the sock like a sponge and does not allow the sock to dry. The cloth or leather top layer of some insoles are provided with tiny, spaced perforations to help channel away the moisture from the sock and provide ventilation, but the moisture is not prevented from being absorbed by the insole and simply flows back through the perforations to the sock. Additional ventilation openings are provided in the insole and/or fabric sides of the shoe in some shoe designs, but most of the moisture is nevertheless permitted to collect and pool in the insole which prevents the sock from drying.
Another problem with the insoles of currently available athletic shoes involves the frictional engagement between the cloth or leather top surface of the insole and the sock and foot of the wearer. In some prior designs, the top layer of the insole is formed of a relatively tacky or sticky material having a coefficient of friction which is higher than the frictional engagement between the sock and foot. Athletic shoes with this type of insole have been found to create blisters on the foot because during use the sock is held in a fixed position against the insole while the foot moves within the sock. The rubbing motion of the foot within the sock creates severe blistering and discomfort.
In an effort to solve the blistering problem described above, athletic shoes have been designed with insoles having a cloth or leather top surface which is relatively slippery or slick compared to the skin of the wearer's foot. These types of athletic shoes help avoid the blistering problem because the foot and sock move as a unit with respect to the slick upper surface of the insole instead of permitting the foot to move within the sock as in the other design described above.
The problem with insoles having a slick top surface is that a condition commonly referred to as "turf toe" often results, particularly on artificial playing surfaces. "Turf toe" refers to a condition involving the fracture of the metacarpalphalangeal joint of the big toe or second toe with attendant damage to the surrounding ligaments. A primary cause of this condition is the repeated, and often violent, contact of the big toe and second toe of the foot with the toe portion of an athletic shoe where the shoe permits the foot and sock to readily slide along the slick cloth or leather top layer of the insole of the shoe.
Accordingly, whereas an insole having an uppermost layer with a relatively high coefficient of friction often results in blistering of the wearer's foot, an insole having an upper surface with a low coefficient of friction permits too much sliding of the foot and sock often resulting in damage to the joints, bones and ligaments of particularly the big toe.